This is definitely only for power users with dozens of installed search engines. But those will surely appreciate it.

This extensions is incompatible to Search Words. When I heard of that extension, I had already implemented it into Organize Search Engines. Differently from Search Words, keywords also work for engines using "post" requests when using Organize Search Engines.

Explicitly compatible extensions are Context Search and searchOnTab. Many other extensions that somehow interact with the search bar of Firefox are probably incompatible.